We propose the build a facility where up to 4000 athymic nude mice can be bred and housed. Nude mice in this facility will be used by investigators in several laboratories for research in four areas of human cancer biology. Hormonally responsive human cell lines will be developed by the method of alternate animal to culture passage. The oncogenic potential of ordinary human disease viruses and of chemicals towards human cells will be determined by using tumor formation in nude mice to detect and select malignant transformants. Nude mice bearing human tumors will provide human antigens and reactive lymphocytes for development of new immunotherapy procedures. The cytotoxic action of novel chemotherapeutic agent will be tested on human tumors passaged in nude mice.